Audio ICs 5-channel graphic equalizer BA3812L The BA3812L is a five-point graphic equalizer that has all the required functions integrated onto one IC. The IC is comprised of the five tone control circuits and input and output buffer amplifiers. The BA3812L features low distortion, low noise, and wide dynamic range, and is an ideal choice for Hi-Fi stereo applications. It also has a wide operating voltage range (3.5V to 16V), which means that it can be adapted for use with most types of stereo equipment. The five center frequencies are independently set using external capacitors, and as the output stage buffer amplifier and tone control section are independent circuits, fine control over a part of the frequency bandwidth is possible, By using two BA3812Ls, it is possible to construct a 10-point graphic equalizer. The amount of boost and cut can be set by external components. Applications Radio cassette players, home stereo systems and car stereo systems. Features 1) Minimizes the number of components required to build a graphic equalizer. 2) Low distortion and low noise. 3) Wide operating power supply voltage range (3.5V to 16V). 4) Low current dissipation (5 mA). 5) Wide dynamic range (VOM = 2.1Vrms / VCC = 8V). 6) Built-in input and output buffer amplifiers. Absolute maximum ratings (Ta = 25C) Recommended operating conditions (Ta = 25C) 445 Audio ICs Block diagram Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 8V, and fin = 1kHz) 446 BA3812L Audio ICs BA3812L Measurement circuit Application example 447 Audio ICs By using more than one IC the following applications are also possible: (1) 10-point single-channel graphic equalizer As shown in Fig. 2, with two ICs it is possible to construct a 10-point single-channel graphic equalizer, 448 BA3812L (2) 7-point stereo graphic equalizer As shown in Fig. 3, with three ICs it is possible to construct a 7-point stereo graphic equalizer. Two BA3812L ICs are used to construct a 5-point stereo graphic equalizer, and two of the active inductor circuits from a third BA3812L are added to each. Audio ICs Solid-state inductor A solid state inductor uses an active element and has the equivalent function of an inductor. The circuit shown in Fig. 4 is used in the BA3812L. This circuit employs two capacitors, a potentiometer, and a bias capacitor as external components, everything else is on the chip. The resonance frequency (fo) and the Q of the circuit are fixed by the values of the external capacitors. BA3812L The resonance frequency is obtained from the following formula: fo (Hz) = 2π 1 R0R1CC0 (R: Ω, C: F) Q is the factor that determines the bandwidth of the frequency. If the amount of boost and cut are the same for the same resonance frequency, the larger the value of Q, the narrower the resonant frequency band. The circuit Q is obtained from the following formula: Q= CR1 CO RO Electrical characteristic curves 449 Audio ICs External dimensions (Units: mm) 450 BA3812L